Soil Analysis

CNF uses soil tests for two functions, chemical residue analysis and mineral analysis.

A chemical residue analysis is usually only required on joining the project. It's used to determine the status, if any, of residues left in the soil from previous land use practices.

A mineral analysis gives a snapshot of the capacity for the soil to hold nutrients and also the nutrient load at the time the sample was taken. CNF recommends that this is undertaken every few years to gauge how the farm soil fertility programme is working. Soil tests are not exact because nutrient availability at any particular time depends on many environmental and climatic factors which are continually varying. This isn't a problem because Nature works well within quite a wide margin for error. Treat the results from the point of view of providing a good basis from which you can assess your current soil fertility and work on improvements if required.

CNF recommends that you don't go to the agricultural fertiliser companies for soil tests. Their results can be worse than useless and targeted to what they want to sell rather than what your soil needs.

We've also prepared a few notes on the important minerals required for healthy plant growth and how to interpret your soil test results at this link on Albrecht Soil Tests.

Soil Sampling

If you need to take a soil sample from your production area(s) for a chemical residue test or mineral assessment and don't know how to go about it, then read on.

Always use a clean spade and bucket to take soil samples. This is especially important if you're sampling for an Albrecht mineral test as the chemical analysis methods are very sensitive. Flaking rust or galvanising on the shovel is virtually guaranteed to show up as a distorted reading for iron and zinc at least.

Be careful if you have more than one soil type in your sampling area. Don't mix them together if you're collecting for a mineral analysis — each soil type will require its own set of samples and a separate test. Also make sure you thoroughly wash down your shovel and bucket between soil types as well. For a chemical residue analysis it shouldn't matter unless you know there have been different land uses in the past.

Preparing a Soil Sample

1. Decide how many samples you are going to take and what your collecting pattern is going to be. As a guide, take about 10 to 20 samples per hectare (or 4 - 8 samples per acre in the old money).
   Make sure that the samples are representative of the area you want tested so, for example, don't take one from where you built the compost heap last year or dropped that bag of lime off the back of the ute.
   The accompanying diagram shows a suggested soil collecting pattern for about a hectare.
   
2. For each collecting site, remove any grass, weeds or loose organic debris from the soil surface.
3. Dig a hole about 100-150mm deep. Take a slice about 30mm thick from a side of the hole and place it in the bucket.
4. When you've collected all of your samples, thoroughly mix them together in the bucket. Take out about 300 grams, remove any rocks and put it into a sealable plastic bag — this is the sample to send off for testing.
5. Place the soil sample into a padded bag with your payment and remember to include a note specifying your name and address and the type of test required. Mail this off to the relevant laboratory, see below.

Soil Testing Laboratories — Contact Details

Chemical Residue Analysis

Albrecht Mineral Analysis